1. Field of the Invention
The present invention relates to an improved electronic control circuit, and more particularly, to an electronic control circuit which provides the functions of a multi-position power switch and a sensor device to control operation of an apparatus.
2. Description of Prior Art
Presently available electric space heaters and electric fans for domestic use are generally provided with at least two control components. The first control component is a multi-position power switch to select a proper setting, e.g. off/high/medium/low. The second control component is a thermostat to de-energize the device when a predetermined, pre-set temperature value is achieved. Likewise currently available humidifiers are provided with a similar multi-position power switch and, rather than a thermostat, are provided with a humidistat to sense when a predetermined, pre-set humidity level is achieved.
The present multi-position power switches and mechanical thermostats/humidistats are expensive, unreliable, and mechanically complex. Additionally, these components constitute as a major portion of the cost and complexity in making and using low cost heaters, fans and humidifiers. Furthermore, the mechanics of these components tend to render them the most oft failed components in the device. More specifically, each component requires a control knob and individual wiring connections, which are labor intensive and points of potential failure.
It is an object of the present invention to provide an electronic control device in a heater, a fan or a humidifier which eliminates the use of complex switches and reduces wiring connections to improve reliability.
It is yet a further object of the present invention to provide an electronic control device in a heater, a fan or a humidifier which is simple to construct thereby reducing complexity of construction and lowering the cost of same.
It is yet a further object of the present invention to provide an electronic control device in a heater, a fan or a humidifier which improves the reliability of the operation.
It is still another object of the present invention to provide a solid state electronic control device which uses a single actuator to set a desired operating level (high, medium, or low) as well as a predetermined temperature/humidity value at which power to the unit is to be terminated.
It is another object of the present invention to provide an electronic control circuit for use in a heater, a fan or a humidifier which uses a single push button to both turn the unit on, set an operating power level and set a predetermined threshold temperature/humidity value to achieve by operation of the unit.
In accordance with one form of the present invention, an electronic control circuit is provided for operating a device such as a heater, a fan, a humidifier or any other device which includes an operating power level and a pre-set value for comparison with a sensor device. The electronic control circuit includes a single control switch for turning on the device and selecting a mode of operation. The mode of operation includes both a power level of operation and one of a plurality of pre-set values. The sensor is provided for sensing a condition. The electronic control circuit further includes a comparator for comparing the sensed condition to the selected preset value. The electronic control circuit includes a means for providing operating power to the device in response to an output from the comparator. In a preferred embodiment, the single control switch is a push-button switch. Furthermore, the means for providing operating power to the device includes an application-specific integrated circuit.
In one embodiment, the electronic control circuit is used in an apparatus for modifying ambient air conditions. The apparatus includes a housing, a fan assembly positioned within the housing and including a motor and a fan blade attached to the shaft of the motor. The apparatus further includes an electronic control circuit electrically coupled to the motor and adapted to provide power thereto. The electronic control circuit has a single switch to turn on operating power to the apparatus and to select a pre-set threshold ambient air condition. The electronic control circuit further includes a sensor for sensing an ambient air condition and a means for comparing the pre-set threshold ambient air condition to the sensed ambient air condition. The electronic control circuit provides power to the fan assembly motor to substantially achieve the pre-set threshold ambient air condition in view of an output of the comparing means and terminates power to the fan assembly motor when the pre-set threshold ambient air condition is substantially attained. Preferably, the switch is a push-button switch and the electronic control circuit includes a plurality of discretely incremented pre-set threshold ambient air condition values which can be selected by repeatedly activating the switch. The apparatus further includes indicia, such as light emitting diodes, to indicate both the power level of operation and the selected pre-set threshold ambient air condition.
The logic for the electronic control circuit is provided by an application-specific integrated circuit to control power to the apparatus motor and to illuminate the indicia associated with the mode of operation. The sensor may comprise a thermistor in the case of a fan, a heater, a griddle, or the like or a humidity sensor for use with a humidifier. With respect to humidifiers, the electronic control circuit can be used with either a cool mist humidifier which utilizes a fan and a wick filter immersed in a pool of water or with a warm mist humidifier which includes a heating element for creating steam to be released to the surroundings.
The present invention is also directed to a method of operating an apparatus for modifying an ambient air condition. The apparatus includes either a heating element or a fan assembly wherein the fan assembly includes a motor and a fan blade coupled to the shaft of the motor. The electronic control circuit is electrically coupled to either the heating element or the fan motor, or both, for providing operating power thereto. The electronic control circuit includes a single control switch and a sensor for sensing an ambient condition. The apparatus is operated by actuating the single control switch to turn on the apparatus and to select an operating power level and a pre-set threshold ambient air condition value. The pre-set threshold ambient air condition is compared to the sensed ambient air condition and operating power is provided to the heating element, the motor or both if the sensed ambient air condition is not substantially similar to the pre-set ambient air condition. Power is terminated to the device when the sensed ambient air condition is substantially similar to the pre-set threshold ambient air condition. The method further includes repeatedly actuating the switch to progress through a plurality of operating modes and pre-set threshold ambient air condition values.
A preferred form of the electronic control circuit, as well as other embodiments, objects and advantages of this invention, will be apparent from the following detailed description of the illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.